Referring to FIG. 1, which is a schematic view showing an existing top-emission OLED display substrate, the top-emission OLED display substrate includes a base substrate 101, and thin film transistors (TFT) 201, 202 and an OLED 203 arranged on the base substrate 101. The OLED 203 includes, in a direction away from the base substrate 101, an anode 107, an organic layer 109 and a cathode 110. Usually, the cathode 110 is made of a transparent or translucent conductive material by sputtering or depositing. The cathode 110 is thin and has a relatively large resistance, so an internal resistance (IR) drop may be induced when it is applied to a large-size OLED display device, resulting in deteriorated image quality of the OLED display device.